Horses commonly develop foot pain from abscesses to bruises but one of the most common reasons for foot pain is laminitis and founder. Horses that develop this condition, regardless of the cause, are in significant pain and some cannot walk or even stand. There are many different treatments for laminitis but one important treatment is to support the sole with something soft to decrease pain but hopefully prevent displacement of the coffin bone. The coffin bone is the bone in the hoof and with severe laminitis, this bone rotates away from the hoof wall, similar to pulling off a person's fingernail.
There are many methods to accomplish this support and many veterinarians use a soft Styrofoam pad that supports the hoof but will compress and help with pain. I have used these Styrofoam pads for years and like them but since they compress, they have to be changed every 24 hours to continue to be effective. Another possibility is to place the horse in a stall with 6 to 8 inches of deep soft sand that will not compact. The concern with this method is that soft sand that will not compact is difficult to find and it takes a truck load of sand to fill most stalls, so sometimes availability is difficult. Dr. Mike Steward from Oklahoma indicates in the International Equine Veterinarian that he uses a pad made of ethylene vinyl acetate or EVA. This material is light weight but durable and deformable, and keeps its shape for weeks. This pad can be taped on the foot and trimmed as needed, depending on the needs of a horse as determined by X-rays. If you have a horse that has foundered, ask your vet about an EVA shoe.